Characterization of brain tumor initiating cells isolated from an animal model of CNS primitive neuroectodermal tumors.

Sergey Malchenko,Marcelo B Soares,Yulia Kostenko,Kiran Velpula,Yingtao Bi,Mary J.C Hendrix,Maheedhara R Guda,Ramana V Davuluri,Jerusha Boyineni,Tadanori Tomita,Naira V Margaryan,Simone T Sredni

doi:10.18632/oncotarget.24460

Abstract

CNS Primitive Neuroectodermal tumors (CNS-PNETs) are members of the embryonal family of malignant childhood brain tumors, which remain refractory to current therapeutic treatments. Current paradigm of brain tumorigenesis implicates brain tumor-initiating cells (BTIC) in the onset of tumorigenesis and tumor maintenance. However, despite their significance, there is currently no comprehensive characterization of CNS-PNETs BTICs. Recently, we described an animal model of CNS-PNET generated by orthotopic transplantation of human Radial Glial (RG) cells - the progenitor cells for adult neural stem cells (NSC) - into NOD-SCID mice brain and proposed that BTICs may play a role in the maintenance of these tumors. Here we report the characterization of BTIC lines derived from this CNS-PNET animal model. BTIC’s orthotopic transplantation generated highly aggressive tumors also characterized as CNS-PNETs. The BTICs have the hallmarks of NSCs as they demonstrate self-renewing capacity and have the ability to differentiate into astrocytes and early migrating neurons. Moreover, the cells demonstrate aberrant accumulation of wild type tumor-suppressor protein p53, indicating its functional inactivation, highly up-regulated levels of onco-protein cMYC and the BTIC marker OCT3/4, along with metabolic switch to glycolysis - suggesting that these changes occurred in the early stages of tumorigenesis. Furthermore, based on RNA- and DNA-seq data, the BTICs did not acquire any transcriptome-changing genomic alterations indicating that the onset of tumorigenesis may be epigenetically driven. The study of these BTIC self-renewing cells in our model may enable uncovering the molecular alterations that are responsible for the onset and maintenance of the malignant PNET phenotype.

Highlights

CNS Primitive Neuroectodermal tumors (CNSPNETs) are members of the embryonal family of malignant childhood brain tumors, which remain refractory to current therapeutic treatments [1].There is a paradigm of brain tumorigenesis that implicates a limited number of genomic and/or epigenomic alterations in the transformation of neural stem cells (NSC) into brain tumor-initiating cells (BTIC) [2,3,4,5]
There is a paradigm of brain tumorigenesis that implicates a limited number of genomic and/or epigenomic www.impactjournals.com/oncotarget alterations in the transformation of neural stem cells (NSC) into brain tumor-initiating cells (BTIC) [2,3,4,5]
The molecular characteristics of BTICs, those of CNS-PNET BTIC, are still largely unknown. As it is imperative from the clinical perspective to investigate PNET BTIC’s function in brain tumor maintenance, we proceeded to isolate cells with NSC characteristics from the tumors originated in our model in order to get insight to the biology of the cells that are presumably responsible for tumor maintenance

Summary

Introduction

CNS Primitive Neuroectodermal tumors (CNSPNETs) are members of the embryonal family of malignant childhood brain tumors, which remain refractory to current therapeutic treatments [1].There is a paradigm of brain tumorigenesis that implicates a limited number of genomic and/or epigenomic alterations in the transformation of neural stem cells (NSC) into brain tumor-initiating cells (BTIC) [2,3,4,5]. It was shown that CNS-PNET BTICs derived from a clinical specimen were able to maintain neuronal and glial differentiation and demonstrated a self-renewal potential - the hallmarks of NSCs [6]. Despite their role in tumor maintenance, there is no comprehensive characterization of CNS-PNETs BTICs to date. We described an animal model of CNSPNET that was generated by orthotopic transplantation of human Radial Glial (RG) cells - the progenitor cells for adult NSCs - into NOD-SCID mice sub-ventricular zone of the brain [7], and proposed that BTICs may play a role in the maintenance of these tumors [8]. We documented expression of RG-BTIC markers such as SOX2, Vimentin and Nestin, BTIC marker OCT3/4, up-regulation of onco-protein cMyc, along with an aberrant accumulation of stabilized tumor-suppressor protein p53 in the model tumors [8]

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